The remit and boundaries of the Macmillan Nursing role in the UK have been called into question recently by a number of policy-driven changes. The rapid appointment of tumour site-specific nurses and the development of posts for palliative medicine, stemming originally from the Calman-Hine recommendations for reorganizing cancer services, have created unparalleled challenges of adaptation to new working practices and procedures. The extent to which Macmillan Nurses are adapting to these new demands was addressed as part of a major evaluation study of UK Macmillan Nursing in 12 sites commissioned by the UK charity Macmillan Cancer Relief. This paper draws upon semi-structured interviews with Macmillan Nurses (n = 44) and their key colleagues (n = 47). We found that differences of expectation between Macmillan Nurses and their managers about the appropriate focus of their work lead to problems of role ambiguity and role conflict; that Macmillan Nurses lack resources with which to develop an educative and consultative role and yet substitute for inadequacies in skills and knowledge of other health care staff; and that problems are associated in co-working with newly appointed cancer site-specific nurses and palliative medicine colleagues. Macmillan Nursing has a crucial role to play in meeting the objectives in the NHS Cancer Plan. However, in order to ensure that their expertise is used efficiently and effectively, there is an urgent need to clarify the nature and scope of the Macmillan Nurse role, to attend to issues of team working and to improve the skills of nonspecialist staff in palliative care.